<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .main{
            width: 500px;
            height: 500px;
            border: 1px solid #000;
            background-color: skyblue;
            display: flex;
            flex-flow: column nowrap;
        }

        .main .box{
            width: 100px;
            /*height: 100px;*/
            background-color: blueviolet;
            flex-basis: 100%;
        }
    </style>
</head>
<body>
    <div class="main">
        <div class="box">
            和其他神秘地区一样
        </div>
    </div>
</body>
</html>
